Biology 0610/51 May/June 2019: question paper and mark scheme
Cambridge IGCSE Biology (0610), Paper 5 Practical Test, May/June 2019. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
You are going to measure the distance moved by different concentrations of citric acid through agar.
You are provided with a Petri dish labelled agar plate.
The agar in the Petri dish contains Universal Indicator which will change colour in the presence of acid.
Read all the instructions but DO NOT CARRY THEM OUT until you have drawn a table for your results in the space provided in 1(a)(iii).
You should use the safety equipment provided while you are carrying out the practical work.
Step 1 Label three test-tubes A, B and C and place them in a test-tube rack.
Step 2 Make three solutions, each containing a different concentration of citric acid, in the labelled test-tubes.
Use the volumes of 5% citric acid and distilled water shown in Table 1.1 to make the solutions.
Table 1.1
test-tube
A B C
volume of 5% citric acid solution / cm3 1.0 2.0 10.0
volume of distilled water / cm3 9.0 8.0 0.0
percentage concentration of citric acid solution 0.5 1.0 5.0
Step 3 Turn the Petri dish over so the base side is up. Use a marker pen to draw three lines to divide the base into approximately equal sections. Label the sections A, B and C as shown in Fig. 1.1.
A
C B
Fig. 1.1
Step 4 Turn the Petri dish so the base side is down. Use a straw to cut a hole in the centre of each section of the agar in the Petri dish, as shown in Fig. 1.2.
Hold the straw vertically and push through the agar to the bottom of the layer. As you remove the straw twist it slightly to pull out the agar. Squeeze the end of the straw gently to push the agar you have removed onto a paper towel.
A
B C
Fig. 1.2
Step 5 Use a pipette to transfer three drops of solution from test-tube A into the hole in the agar in section A of the Petri dish.
Do not let the solution drip onto the surface of the agar.
Step 6 Use a clean pipette to repeat step 5 for the solution in test-tube B and the hole in the agar in section B of the Petri dish.
Step 7 Use a clean pipette to repeat step 5 for the solution in test-tube C and the hole in the agar in section C of the Petri dish.
Step 8 Start the stop-clock and leave the Petri dish for five minutes.
Step 9 After five minutes observe the appearance of the agar around each of the holes.
(a) (i) Describe the appearance of the agar around the holes in A, B and C after five minutes.
…… [1]
Step 10 Leave the Petri dish for a further 25 minutes. During this time, continue with the other questions.
Step 11 After a total of 30 minutes use the ruler to measure the distance the citric acid has travelled from the edge of the hole in section A. You may need to use the hand lens.
Record your results in the table you have prepared in 1(a)(iii).
Step 12 Repeat step 11 for the holes in section B and section C of the Petri dish.
(ii) Describe how you decided where to measure the distance travelled by the citric acid solution.
…… [1]
(iii) Prepare a table to record your results.
You should include:
• the concentration of the citric acid solutions
• the distance moved by each solution in the agar.
Record your results in the table as you carry out the practical work.
[4]
(iv) State a conclusion for your results.
…… [1]
(v) The citric acid moves through the agar by diffusion. The diffusion coefficient is used to show the effect of concentration on diffusion.
The formula to calculate the diffusion coefficient is:
(distance travelled)2 diffusion coefficient = time
Calculate the diffusion coefficient for a 10% solution of citric acid that travelled 14 mm in
30 minutes.
Give your answer to two significant figures.
Space for working.
…… mm2 per minute
[2]
(b) (i) State two variables that have been kept constant in this investigation.
1 ……
2 ……
[2]
(ii) Identify one source of error in this investigation and suggest how the error could affect the results.
error ……
effect on results ……
[2]
(c) Describe how you could adapt this method to find the effect of temperature on the rate of diffusion. Agar melts at 70 °C.
…… [6]
[Total: 19]
Mark scheme
1(a)(i) (agar closest to the well is) pink / red / orange / yellow ; 1
1(a)(ii) from (edge of) hole to (edge of) the (red or yellow) 1
circle / zone ;
diameter / radius of (red or yellow) circle ;
1(a)(iii) table drawn with header line and at least two columns ; 4
headings: concentration of citric acid and distance
/ diameter ;
units in headers only; percentage / % and mm / cm ;
three distances recorded in correct column / row ;
1(a)(iv) the higher the concentration (of solution) the further (the acid) 1
moves / AW;
1(a)(v) 6.5 ;; 2
1(b)(i) number of drops / three drops (of citric acid / solution in the 2
holes) ;
agar , concentration / depth / volume / type ;
holes/wells, depth/size/width ;
indicator, concentration / volume / type ;
time / 30 minutes ;
same temperature ;
AVP ; e.g. same type of acid/volume of stock solution
1(b)(ii) 2 AW throughout
error effect on results mark as a pair, effect must match the source of error
drop sizes vary ; larger volume produces
greater diffusion distance ; ora
no repeats ; unable identify anomalous
results ;
one dropping pipette used a weaker solution would
for all (three) solutions produce a smaller diffusion
/ contamination ; distance ;
longer diffusion greater / lesser distance
time / citric acid added at travelled ;
different times / circles
measured at different
times ; ora
difficult to judge edge of results overestimated or
colour change / subjective underestimated ;
;
uneven shape / not distance moved may be
circular ; more/less than measured ;
difficult to cut holes ; greater / less, surface area or
volume contained may have
less effect on distance ;
spillage ; area may be larger ;
AVP ; e.g. solutions not AVP ; more / less concentrated
mixed so diffuse more/less
1(c) any two from given method ;; 6
• agar plates used
• indicator (in agar)
• holes made in agar
• (citric) acid added
• left for fixed (stated) time
• measure distance moved/diameter/radius
any three from novel method ;;;
• using range of at least 2 temperatures
• temperatures specified and all less than 70 (°C)
• idea of keeping temperature constant
• ref to temperature equilibration time prior to adding citric
acid
• measure time taken to reach specified diameter
any additional points:
same concentration of citric acid ;
wear gloves / goggles ;
repeating the investigation at least twice / three holes in each
plate / use three dishes at each temperature ;
AVP ;
(a) Fig. 2.1 is a photomicrograph of a cross-section of part of a leaf.
A
B
magnification ×100
Fig. 2.1
(i) Draw a large diagram to show the layers present in the leaf section shown in Fig. 2.1.
Do not draw any cells.
[3]
(ii) Measure the thickness of the leaf along the line AB on Fig. 2.1.
length of line AB ……
Calculate the actual thickness of the leaf using your measurement and the formula.
Include the units.
length of line AB on Fig. 2.1 magnification = actual thickness of leaf
[3]
(iii) Fig. 2.2 shows a photomicrograph of cells from one type of tissue found in leaves.
magnification ×300
Fig. 2.2
Label the layer on your drawing, with the letter X, to show where this type of tissue is found. [1]
(b) Scientists carried out an investigation into the effect of light on the growth of leaves.
Plants of the same species (A) were grown in three different light intensities.
The plants were grown in the same soil and kept in glasshouses with automatic watering.
A sample of 100 leaves was selected at random and collected from plants in each of the three different light intensities. A total of 300 leaves were collected.
The scientists studied the variations in the size and structure of the leaves in each sample.
(i) Suggest why the scientists used large samples of leaves.
…… [1]
(ii) Suggest why the leaves in each light intensity were selected at random.
…… [1]
(iii) A grid, divided into millimetre squares, was used to measure the surface area of the leaves.
Outline how the grid could have been used.
…… [2]
(iv) State the variable that was changed (independent variable) in this investigation.
…… [1]
(c) The scientists collected data from one other plant species (B).
Table 2.1 shows the results.
Table 2.1
light intensity average leaf area / mm2
/ arbitrary units species A species B
100 3600 2800
50 3900 3400
10 6500 2900
(i) Calculate the percentage difference in the average leaf area for species A from a light intensity of 50 arbitrary units to 10 arbitrary units.
Show your working and give your answer to the nearest whole number.
…… %
[2]
(ii) Plot a bar chart on the grid to show the average leaf area for species A and B, at each light intensity.
[4]
(iii) Describe the trends shown in your graph for species A and species B.
…… [2]
(iv) The scientists want to determine more precisely the light intensity that results in the largest leaf area for species B.
Suggest how the method used in the investigation could be modified to achieve this.
…… [1]
[Total: 21]
Mark scheme
2(a)(i) line: clear single continuous lines without shading ; 3
size: occupies at least half the space available ;
detail: layers in correct proportions ;
2(a)(ii) length of line AB = 40 mm ; 3 A ±1 mm
actual length =0.4 mm ;; A ±0.01 mm
2(a)(iii) X written on the spongy mesophyll of drawing ; 1
2(b)(i) to obtain a representative leaf size ; 1
to identify anomalous results ;
2(b)(ii) to avoid bias / gain a representative sample / AW ; 1 A leaves at different heights may be different sizes
so that a comparison can be made (between the different
light intensities) ;
2(b)(iii) draw round the outline of the leaf on a grid / place leaf under a 2
(transparent) grid ;
count the squares ;
include any squares more than half covered / other valid
method described ;
2(b)(iv) light intensity ; 1
2(c)(i) 67(%) ;; 2
2(c)(ii) axes labelled with units: 4
light intensity / arbitrary units or au
and average leaf area / mm2
and species A and B labelled / key given ;
scale and size:
even scale for leaf area
sequential for x-axis
bars/plotting area to occupy at least half the grid in both
directions ;
plots:
6 values plotted accurately ± ½ small square ;
4 bars:
bars the same width (at least 1 small square wide)
gaps present between bars /pairs of bars ;
2(c)(iii) species A: 2
as the light intensity decreases the (average) leaf area
increases / ; ora
species B:
(average) leaf area increases with increasing light intensity
(to maximum at 50 au) and then decreases ; ora
2(c)(iv) measure leaf growth at a narrower range of light intensities 1
around 50 (au) ;
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On this page, free: the mark scheme for IGCSE Biology 0610/51, May/June 2019 (0610_s19_ms_51), and the question paper (0610_s19_qp_51), to read or download, with each question's marking points written out underneath.
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Biology 0610/51 for May/June 2019 is out of 40 marks, with 1 hour 15 minutes to answer it, across 2 questions.
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